This invention relates to flip chip packaging and, more particularly, to providing a Au/Sn alloy interconnection between a chip and a substrate.
Conventional methods for interconnecting a flip chip to a substrate include an Anisotropic Conductive Film (ACF) with Ni or Ni/Au coated polymer particles in which a contact type interconnection is made. Fragments of the polymer film which remain trapped at the interconnection point often lead to poor electrical contact and reduced reliability of the package. Additionally, the polymer film reduces the reliability of the bonding interface during the chip bonding process. Conventional flip chip techniques that use either ACF, Non-Conductive Adhesive (NCA) or Non Conductive Polymer (NCP) also suffer from problems in curing the adhesive on adjacent bonding sites on a substrate during the chip bonding process.
What is needed is a flip chip structure and method that provides for metallurgical interconnection between the flip chip and the substrate and that further provides for improved bonding between the chip and the substrate.